?????????
      +----------
37B49 | B0BB350A6
       -43370
        =====
        7B5AA5
       -7411A4
        ======
          4B900
         -43370
          =====
           5816A
          -37B49
           =====
           7B7A46
          -7411A4
           ======
           ??????

base: 12
letters: 0123456789AB
difficulty: intermediate
missing: 2